There are two ways to do this problem. One way is the cowardly way they teach in school using a graph in that case look below to see that the range is,Originally Posted byKiwigirl

The second way. The function is defined as the inverse function of the function,

. Now there is a rule that the range of the inverse function is the domain of the orignal function. Since the domain of the original function is thus the range of is

There is actually a third way (much more advanced). Find all such such as the equation has a solution.